The present invention relates to an electromagnetic diaphragm disk actuator.
Actuators of the diaphragm disk type are particularly useful in an outer-space environment, such as in satellites or the like when, for example, an antenna must be adjusted by very small angles with high angular resolution. The number of electromagnet pairs which must be successively excited for each adjustment process is dependent upon the amount of control one desires to have over the adjustment regulation. In order to obtain a given regulating quantity, the electromagnet control has a storage system which stores, following the switching off of the electromagnets, the information relating to the particular electromagnet pairs which are to be excited first for the next regulating process, so that the start of the new regulating distance coincides with the end of the preceding regulating distance.
In a known diaphragm disk actuator (German Offenlegeungschrift No. 2,525,036) the diaphragm is constructed as a circular disk. The rotor is provided with an axial toothing or gear teeth on the side of its circumferential edge facing the electromagnets which corresponds to the axial toothing or gear teeth arrangement on the annular rolling path for the disk on the stator. The number of teeth between the axial toothings varies by an even number and the diaphragm is axially deflected by the simultaneous excitation of a pair of diametrically opposed electromagnets such that its teeth mesh with teeth in the rolling path at diametrically opposed locations. As a result of the stepwise excitation of successive pairs of electromagnets, the meshing points of the teeth travel in a circle leading to a relative rotation of the rotor with respect to the stator on the basis of the different numbers of teeth. However, as meshing only takes place upon exciting the electromagnets, there is no holding moment for the rotor when the electromagnets are deactivated. Consequently, there is an undesired adjustment of the rotor due to vibrations or accelerative forces as will occur upon launching of a rocket, which is not recorded by the electromagnet control store. Thus, regulating errors occur when the motor is activated.
Another known diaphragm disk actuator, in U.S. Pat. No. 4,081,702 (German Auslegeschrift No. 2,517,974), discloses that when the electromagnets are not excited, the engagement of the diaphragm holding teeth in the tooth holding rim produces a holding moment for preventing an undesired shifting of the rotor when the motor is switched off. According to this known actuator, the diaphragm is kept deformed to a cone-shaped shell under elastic pretensioning due to the position of the toothed holding rim. However, the diaphragm is driven by frictional resistance with the side of its circumferential edge remote from its holding teeth on the stator rolling path. Due to this rolling of the circumferential edge of the diaphragm on the rolling path in response to successive excitations of the electromagnet pairs, the meshing points between the holding teeth of the diaphragm and the toothed holding rim are respectively displaced by 90.degree. relative to the diametrically opposed engagement points of the circumferential edge of the diaphragm on the rolling path in order to rotate with the engagement points in a shaft-like manner.
The necessary elastic dimensional changes of the circumferential edge of the diaphragm at the meshing points of its holding teeth with the toothed holding rim must be brought about at circumferential points displaced by 90.degree. relative to these meshing points due to the elastic deflection of the circumferential edge of the diaphragm. The diaphragm circumferential edge must be made relatively rigid to achieve this effect with the conical shape of the diaphragm. This relative rigidity insures that the circumferential stresses which are present to a considerable degree in the diaphragm due to the conical pre-deformation are not increased to such an extent by the deflection of the circumferential edge that they lead to the bulging of the diaphragm, and consequently, to regulating errors. However, rigidity of the circumferential edge necessitates relatively powerful, and therefore, heavy electromagnets in order to effect local deflection of the circumferential edge of the diaphragm by the magnetic force.
Additionally, the operating moment or torque of this conventional motor is fundamentally determined by the rigidity or pretensioning force of the diaphragm because the force acts circumferentially via the tooth flank angle of the holding tooth system which produces the holding moment and the operating moment. The moment produced by the frictional resistance rolling of the diaphragm on the rolling path must be kept small. A high moment would result in slip occurring on each side of the diaphragm due to the unavoidable tolerances even with optimum adaptations of the thrust movements, which can lead to stepping errors. Thus, the operating moment of this conventional motor cannot be increased by a higher power expenditure.